Nickel azobenzene complex

Fig. 3.3 Example of a ic-bonded azobenzene nickel complex 3.7 (bis (/-butyl isocyanide)...

The reaction of di-7r-cyclopentadienylnickel and azobenzene gives a purple-blue crystalline nickel complex, mp 118-119°. Based on the following data, structure [5-50] was assigned to the compound. Elemental analysis... 

Whilst C—H bonds represent the most ubiquitous chemical linkage in Nature, they are at the same time some of the most difficult bonds to cleave, although they are not completely inert [5b,c]. For example, in 1963 Kleinman and Dubeck reported the possibility of C—H bond cleavage in azobenzene by the Cp2Ni complex (Scheme 13.1) [1]. The structure originally proposed by Kleinman and Dubeck considered the nickel center to be coordinated T 2 to the N=N n-bond (2) (Scheme 13.2). 

Together with azobenzene, other diaryldiazenes have also been found to form complexes with nickel(O) and PEt3. All the complexes are air-unstable and have been prepared in rigorous anhydrous and oxygen-free conditions according to equation (41).210... 

Aryldiazenato complexes of nickel(0) have been prepared using reaction (38) at —78 °C with the neutral azo molecules tetrachlorodiazocyclopentadiene (N2QCI4) and diazofluorene (N2C13H8) in the place of azobenzene.209,211... 

In 1971, Otsuka etal63,64, and Klein and Nixon65 simultaneously reported the formation of nickel 7r-complexes of azobenzene. The tr-bonded structure (type IV, Fig. 3) was assigned on the basis of displacement reactions and spectroscopic evidence. Treatment of (jr-Ph—N=N-Ph)Ni (PR3)2, (R = Me, Bu, Ph), with aqueous ethanol or with dimethylglyoxime in THF resulted in the reduction of the diazeno... 

The intermolecular bonds of N=N jt-electrons to metal were, however, reported as a 7t-bonded azo-transition complex 3.7 (bis(tert-butyl isocyanide)(azobenzene)nickel) by Dickson and Ibers in 1972 as shown in Fig. 3.3 [15]. 

Other reducing agents such as NaBH4 and LiAlH4 also open carbon-metal bonds. One elegant application was in the structure determination of azobenzene complexes of nickel, palladium, and platinum 119, 120). 

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